1. Field of the Invention
The present invention relates to a light-emitting device using luminescence such as electroluminescence, and more particularly relates to a light-emitting device with a light-emitting element that is formed by interposing a light-emitting layer between a pair of electrodes.
2. Description of the Related Art
A display device including a light-emitting element (hereinafter, referred to as a light-emitting device) has advantages such as wide viewing angle, low power consumption, and rapid response speed as compared with a liquid crystal display device, and research and development thereof have been actively carried out.
The light-emitting element has a structure of a luminescent material provided between a pair of electrodes, and light from the luminescent material is extracted depending on the light-transmitting properties of the electrodes.
For example, in the case of desiring to extract light toward one direction, a light-transmitting material is used for one electrode provided in the direction where light is extracted whereas the other electrode is formed by using a material that has no light-transmitting property, that is, a reflective material. The light extraction efficiency can be enhanced by using reflection at the other electrode effectively.
At the same time, when this reflective material is used for the electrode, reflection of outside light becomes a problem. In order to prevent reflection of outside light, a structure provided with a polarization plate or a circular polarization plate should be considered. However, there is fear that light from the light-emitting element is lost when a polarization plate or the like is used.
As a method for preventing reflection of outside light, a display device is proposed, where the optical distance between a pair of electrodes is made to satisfy a given formula, a resonator structure is introduced, and the resonance wavelength coincides with the peak wavelength of a spectrum of light to be extracted (refer to Patent Document 1).    [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-178930